The open and the patent literature on sol-gel processing of silica containing materials is extensive. Most of the chemical compounds used as a precursors to silica containing materials are either tetramethoxy or tetraethoxy silanes (TMOS or TEOS). These precursor materials combined with either an acid or base catalyst and water to hydrolyze the precursor to form a variety of silica-containing materials. Polymeric silica contains residual alkoxy groups that can be used to form thin films or spinning fibers or used for processing mesoporous silicas or zeolitic materials with the addition of template molecules. Also, secondary alkoxides of other metals for example aluminum, titanium, hafnium and zirconium alkoxides may be added to make mixed-metal sol-gel derived “hybrid materials.”
Alternately, organic monomers or polymers or organic functionalized silicon alkoxides such as R—Si(OEt)3 or R2Si(OEt)2 may be used to introduce organic groups into the resulting mixed-metal sol-gel derived “hybrid materials.” Organic/Inorganic Hybrid Materials, MRS Symp. Ser. Vol. 519, R. M. Laine, C. Sanchez, C. J. Brinker, E. Giannelis eds. December 1998; Organic/Inorganic Hybrid Materials 2000, MRS Symp. Ser. Vol. 628, R. M. Laine, C. Sanchez, and C. J. Brinker, eds. Mater. Res. Soc., 2001; Organic/Inorganic Hybrid Materials 2002, MRS Symp. Ser. Vol. 726, C. Sanchez, R. M. Laine, S. Yang and C. J. Brinker, eds. Mater. Res. Soc., December 2002; D. W. Schaeffer, Science 243 (1989) 1023-1027.
Precursors of silicon based materials are typically not water soluble and must be hydrolyzed in a solvent that allows them to become miscible in water so that efficient hydrolysis can be obtained. For example, TMOS and TEOS are typically hydrolyzed in water/MeOH or EtOH mixtures to create a single phase solution. Occasionally, researchers have made modified precursors by treating TMOS or TEOS with ligands that transform them into water-soluble materials. TMOS or TEOS are reacted with ethylene glycol or propylene glycol and a catalyst to form water soluble alkoxides that are hydrolyzed to produce silica-modified hybrid materials or mixed metal systems and/or mesoporous materials. See, for example N. Hüsing and U. Schubert, “Formation and Structure of Porous Gel Networks from Si(OMe)4 in the Presence of A(CH2)nSi(OR)3 (A) Functional Group) Chem. Mater. 1998, 10, 3024-3032; V. Torma, H. Peterlik, U. Bauer, W. Rupp, N. Hüsing, S. Bernstorff, M. Steinhart, G. Goerigk, U. Schubert, “Mixed Silica Titania Materials Prepared from a Single-Source Sol-Gel Precursor: A Time-Resolved SAXS Study of the Gelation, Aging, Supercritical Drying, and Calcination Processes,” Chem. Mater. 2005, 17, 3146-3153; D. Brandhuber, V. Torma, C. Raab, H. Peterlik, A. Kulak, Nicola Hüsing, “Glycol-Modified Silanes in the Synthesis of Mesoscopically Organized Silica Monoliths with Hierarchical Porosity,” Chem. Mater. 2005, 17, 4262-4271; S. Hartmann, D. Brandhuber, N. Hüsing, “Glycol-Modified Silanes Novel Possibilities for the Synthesis of Hierarchically Organized (Hybrid) Porous Materials,” Acc. Chem. Res. 2007, 40, 885-894; M. Weinberger, “Organosilica Monoliths with Multiscale Porosity: Detailed Investigation of their formation and their potential as ceramic precursors,” Dokter der Wissenschaft, Nov. 9 (2009); M. Weinberger, S. Puchegger, T. Fröschl, F. Babonneau, H. Peterlik, N. Hüsing, “Sol-Gel Processing of a Glycolated Cyclic Organosilane and Its Pyrolysis to Silicon Oxycarbide Monoliths with Multiscale Porosity and Large Surface Areas,” Chem. Mater. 2010, 22, 1509-1520; T. Nakamura, H. Yamada, Y. Yamada, A. Gürtanyel, S. Hartmann, Nicola Hüsing, K. Yano, “New Strategy Using Glycol-Modified Silane to Synthesize Monodispersed Mesoporous Silica Spheres Applicable to Colloidal Photonic Crystals, Langmuir 2010, 26, 2002-2007; Y. Suzuki, M. Kakihana, “New Water Soluble and Handy Silicon Precursor for Synthesis of (Y,Ce,Gd)2SiO5 Phosphor,” IOP Conference Series: Materials Sci. and Eng. 2009, 1 012012; K. Matsumara, M. Asai, S. Ichinohe, “Preparation of Water-Soluble Organic Silicon Compounds,” U.S. Pat. No. 6,077,966, Jun. 20, 2000; and H. Eck, M. Roth, “Aqueous redispersible powders which contain a water-soluble polymer and at least one organic silicon compound and process for preparing the same.” U.S. Pat. No. 4,704,416 November 1987.
These examples use alkoxysilanes derived primarily by the direct reaction of alcohols with silicon metal as suggested in reaction (1) below wherein some form of catalyst is used to promote the reaction. Occasionally, the alkoxy silane Si(OR4) is made by a more expensive route, reaction (2), that requires handling toxic and polluting SiCl4. It is important to note that SiCl4 is prepared from reaction of Si metal with HCl, as in reaction (3). Silicon metal is made by carbothermal reduction of SiO2 and carbon as suggested by reaction, (4), however the exact process is more complex and the yields are not quantitative.
SiCl4+4RONa→4NaCl+Si(OR)4  (2)Si+4HCl→2H2+SiCl4 and/or HSiCl3  (3)

Furthermore, the cost of making Si(OR)4 and the resulting commercial production of precipitated silica is usually prohibitive because of the carbothermal reduction step. An exception is the production of precipitated silica used for polishing silicon wafers for chip manufacture where purities equal to or greater than 99.999999 (“eight 9s”) are needed and TMOS or TEOS can be distilled to these purities.
For these reasons, existing processes that use TEOS (or TMOS) or water soluble silica modified materials derived by substitution as shown in reaction (5) are usually mere academic exercises that are not suitable for large scale, efficient, commercial use.

To date, little commercial motivation exists to develop synthetic/processing routes to large quantities of precipitated silicas from these alkoxysilanes because of the multistep, high temperature reaction costs of the starting materials. Consequently, the major route to precipitated silicas is the series of reactions (6)-(8):

This typical industrial process scheme used to make 1000 ton/year quantities of precipitated silica is shown in FIG. 1. Note that considerable CO2 is released into the atmosphere during this process. In addition, considerable amounts of Na2SO4 are produced as waste products that must be disposed of, thereby adding to the costs of the process.
Referring to FIG. 1, the first reaction step produces molten sodium silicate at high temperature that is thereafter acidified with an acid such as H2SO4. The result is an aqueous solution of sodium sulfate and some form of silicic acid, such as Si(OH)4 or oligomers thereof.
This is a high temperature process requiring stoichiometric amounts of base and acid to effect precipitation. Precipitation occurs in an aqueous environment that produces large concentrations of byproduct salts such Na2SO4. The resulting silica powders such as HISIL 223 have salt contamination typically less than 2 wt %.